EVBob
Posts: 44
Joined: Tue Apr 18, 2017 6:06 am

Any advantage to getting a 40 amp charger vs a 32 amp?

Wed Apr 19, 2017 8:44 am

Greetings All,

I have a 50 amp circuit in my garage that came with the house :-)

I could put a (more expensive) 40 amp charger on it. However, would there be any advantage to this? It should charge at the same rate as a 32 amp charger for the i3?

I was thinking it would help "future-proof" if I got a larger charger - however, if down the line we upgraded to something with a bigger battery/bigger inverter - those extra 8 amps won't really help that much? I would probably need to upgrade the circuit to be 60 or maybe even 80 amps to get the full charging speed?

With those thoughts - I really should just get a 32amp charger, and not sweat it?

bmwquickspeed
Posts: 7
Joined: Thu Apr 13, 2017 9:51 am

Re: Any advantage to getting a 40 amp charger vs a 32 amp?

Wed Apr 19, 2017 2:55 pm

I keep thinking the same thing. I was considering going all out and getting the Juicebox 75amp but I don't think I'll bother.

My thinking is that why future proof your home charger when the chances you'll need it to be fast should diminish as charging infrastructure improves. Also your new car will probably have a greater range where a full charge may be less necessary.

Currently I charge at home and at work with the Level 1 charger that came with the car and it has been enough that I have only had to charge at a Level 2 stations maybe 2 times in the 3 years I owned my Nissan Leaf and now that I have an i3 I am still thinking I probably don't need it.

I guess everyones needs will vary but for me I was able to fast charge for the first time last week and there seems to be enough fast charge options that if I am ever in a situation where charging at home and work are not enough at Level 1 I can just Level 3 charge as there are plenty of options close to me.

In my option save your money and get what will work best for your current situation.

jadnashuanh
Posts: 3344
Joined: Thu May 22, 2014 2:07 pm
Location: Nashua, NH USA

Re: Any advantage to getting a 40 amp charger vs a 32 amp?

Wed Apr 19, 2017 7:00 pm

If you have a 50A circuit, I'd seriously consider going with a 40A unit. But, you're right, the current i3 cannot take advantage of the additional charging capacity, but it won't hurt anything except maybe your wallet. The Tesla comes with either a 48A or 72A on-board charging circuit. Cars of similar sized batteries might go that large, but it does come at a cost less expensive units may not want to endure. Lots of homes cannot support an EVSE that large without major upgrades, many people won't want to support, either. 40A * 240V = 9600watts. Say you have an 80Kw battery in a new car...80000/9600=a bit over 8-hours, assuming it's 100% efficient, and it certainly isn't. So, given say a 32A unit with the same battery, at 7680w, that 80000/7680 = 10.5 hours, again, it would take longer, but you get the idea.
Jim DeBruycker
2011 535i x-drive GT, 2014 i3 BEV

archieb
Posts: 44
Joined: Tue Jan 20, 2015 10:00 am
Location: Wisconsin

Re: Any advantage to getting a 40 amp charger vs a 32 amp?

Fri Apr 21, 2017 7:27 am

My EVSE is 5 years old and was originally purchased to charge a Volt. As such it is only a 16A unit. I've used this unit on the i3 for over 2 years and been very satisfied. Compared to a L1 EVSE, even just 16A is a big improvement both in time and the increased efficiency of L2 charging.

I would recommend getting a unit that matches the majority of the usage of your vehicle and any time constraints you may have. I rarely use more than 50% of battery capacity, have 8 hours of low cost charging time, and the 16A EVSE recharges the i3 without a problem. If you routinely use 75% or more of your battery capacity a 32A is more appropriate.

As for future proofing, I believe EVSEs do wear out and are subject to failure as they age. I already had a internal connection failure (heat) which I was fortunate to fix and the EVSE has been functioning without a problem for about 8 months. Heat can be a major contributor to EVSE failure and the higher the load the more potential for heat buildup. I would expect an EVSE to last somewhere between 6 and 10 years and will upgrade when this unit starts to fail.

Archie

jadnashuanh
Posts: 3344
Joined: Thu May 22, 2014 2:07 pm
Location: Nashua, NH USA

Re: Any advantage to getting a 40 amp charger vs a 32 amp?

Fri Apr 21, 2017 12:20 pm

Regarding internal heat of an EVSE...one built to operate at higher currents, but only being used (now) for smaller ones, would tend to mean less heat would be generated, and therefore the potential of longer life. FWIW, the only real load related thing that changes between different EVSE outputs is the power contactor's current rating (essentially, a big relay). Those with higher capacity will have larger contacts that can source higher currents without excessive internal resistance.

FWIW, I'm a big proponent of putting whole home surge suppression at the power panel. There are numerous companies that make these, and they have various response rates and clamping capacity. IF you're going to be making panel changes, IMHO, it is an easy add-on expense to throw one of those into the mix. They can either be installed pre-main breaker, or (probably easier) post main breaker with a dual pole CB dedicated to the thing. Long-term reliability of electronic components is sort of like chopping at a big tree with a small hatchet...over time, you degrade the components with each successive spike verses maybe a big chop if you get a higher current one from a near-by lightning strike. Cheap insurance for everything in your home, or at least those things on that panel.
Jim DeBruycker
2011 535i x-drive GT, 2014 i3 BEV

EugeneM
Posts: 9
Joined: Sun Apr 16, 2017 7:51 am

Re: Any advantage to getting a 40 amp charger vs a 32 amp?

Fri Apr 21, 2017 1:29 pm

I drive a Tesla and got an i3 for my wife. For the Tesla I use a regular nema 14-50 50a outlet I had an electrician install outside and using the standard charge cable supplied by them. It's been fine for the last 2 years.

Since the i3 can't just plug into the nema (why is that again?) I got a 40A juicebox that plugs into the nema outlet and I'll install it next to the outlet myself (by install I mean screw it into the side of the house).

This way I can either unplug the juicebox and plug in my Tesla when I need to charge or just use the level 2 for the i3 and the same connector with an adapter for the Tesla.

I went for the 40a EVSE so I could take full advantage of the Tesla charging capabilities (I currently charge it at 40a on a 50a circuit) AND full advantage of the i3 charging capabilities.

Obviously this doesn't apply to everyone, just my $0.02 :)

EVBob
Posts: 44
Joined: Tue Apr 18, 2017 6:06 am

Re: Any advantage to getting a 40 amp charger vs a 32 amp?

Sat Apr 22, 2017 10:29 am

Thank you everyone for chiming in!

It turns out the 40A Juicebox (non Pro) is about the same price or cheaper than 32amp chargers from other manufacturers....

In the end I decided on a refurbished Juicebox 40A Pro that turned out to be even less price than a new non pro 40A. For others that may be interested in a refurbed or lightly used unit from Juicebox - you just need E-mail them and ask - their Customer Support personnel: Kris is really helpful!

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